1. Field of the Invention
This invention relates to printing presses such as those of the lithographic type and in particular to means for dampening the distribution roller of such presses.
2. Description of the Prior Art
The prior art discloses various systems for depositing a dampening solution onto the distributor roller of a printing press.
Strawn, U.S. Pat. No. 1,438,408 discloses a moisture supplying device for a lithographic printing machine. Strawn""s primary moisture roller is a perforated drum covered with absorbent material. Water is dispersed to the interior of the drum through the apertures and into the absorbent material to be transferred to the surfaces to be dampened. Strawn does not use air to transfer fountain solution to a distributor roller, the moisture roller does not oscillate and it is not a non-contact dampening system.
In Hauser, U.S. Pat. No. 2,622,520, compressed air is blown through a continuously wetted sieve and then a slot for moistening the printing plates. The action is not rotary and, therefore, not continuous. Large amounts of over-spray would be produced.
Koch, U.S. Pat. No. 2,689,523 utilizes a radially perforated, continuously wet hollow cylinder through which compressed air is blown, for moistening an adjacent roller. A shield is positioned between cylinder and roller to ward off unwanted compressed air. The cylinder is not oscillated.
In Warozak, U.S. Pat. No. 3,143,065, the dampening unit includes a cylindrical screen which is rotated through the fountain solution. The unit further includes a cylindrical manifold with an air discharge slot for blowing air onto the screen and discharging solution therefrom onto a printing surface plate.
Paulson, U.S. Pat. No. 3,990,365 discloses a device for moistening the plate cylinders of offset printing machines. An inner rotatable sleeve provides air through radial air passages towards a fixed outer cylinder with spaced apertures. Dampening fluid is fed through gravity onto the outer cylinder. The rotatable inner sleeve forces air outward to direct the fluid to a diffuser which breaks the stream into a spray which in turn is directed to a dampening cylinder.
Harris, U.S. Pat. No. 4,010,686 describes a dampening device for a lithographic offset rotary printing press in which a cylindrical roller, which is in contact with a dampening fluid reservoir, has an apertured peripheral wall. Air jets from a fixed interior flow tube direct air towards the interior wall of the roller and through the apertures, directing the fluid on the roller fluid toward another roller.
Jeschke et al., U.S. Pat. No. 4,188,882 disclose a dampening unit for offset printing machines in which a screen cylinder receives dampening medium from one cylinder and delivers it to another. The screen cylinder is a perforated tube covered by a mesh fabric blanket for carrying the dampening medium. The screen cylinder is mounted on a blow tube disposed eccentrically to the axis of rotation of the screen cylinder and is provided with jet orifices adjacent to the screen cylinder interior wall. A coaxial air supply tube supplies air to the blow tube through a series of orifices.
U.S. Pat. No. 5,036,761 to Wingo describes a press dampening apparatus that includes a water feed roller comprising a stainless steel cylindrical wall having a matrix of water feed apertures that direct water to water form rollers, the feed apertures having ball check valves which are opened through contact with the water form rollers.
Boelkins, U.S. Pat. No. 5,797,983 pertains to a contact lubricator utilizing a perforated roller to allow liquid to migrate to an absorbent material. The liquid is forced through the perforations under pressure. The absorbent material comes in direct contact with the surface to be lubricated.
Koch, German Pat. No. 880,309 discloses a dampening unit comprising a rotating screen cylinder which dips into a fluid supply tank, absorbing liquid into the screen mesh of the cylinder. Compressed air from the inside of the cylinder blows the liquid out, spraying it onto an adjacent roller.
An object of the invention is a non-contact dampening means for a printing press of the lithographic type.
Another object is such a means that can be retrofitted to any lithographic printing press.
Still another object is such a means that uses low pressure air for transfer of dampening solution from the dampening means to the distribution roller of a lithographic printing press.
A further object is such a means that produces consistent and even transfer of dampening solution to the press distributor roller.
These and other objects, features and advantages are accomplished in accordance with the teachings of the present invention, one illustrative embodiment of which comprises a dampening means for use in dampening the distribution roller of a printing press of the lithographic type that includes: a hollow, perforated roller adjacent to the distribution roller; a dampening solution source, containing dampening solution, a variable speed power mechanism for driving the perforated roller through the dampening solution source; an air source for blowing dampening solution obtained from the source onto the distribution roller and an oscillator for oscillating the perforated roller, laterally of the air source as the perforated roller is being rotated.